Masts in the form of periscopes and antenna in the sail of a modern submarine are protected from ice and debris by a protective closure. Before such a mast is raised, the closure must open and be stowed out of the way to allow vertical travel by the mast. In addition, when the mast is up or in the extended position, the closure door must be prevented from closing on the mast. Usually, an operator actuates a mast and closure system by switching circuits and valves in the proper sequence. The operator uses input data from mast position indicators and closure position indicators to evaluate the situation and perform the step-by-step actuation sequence. Operation in the wrong sequence may result in damage to and perhaps catastrophic failure of both the mast and closure mechanisms. The current state of the art has concerned itself with mechanical go-no-go linkages and devices which permitted only a set chain of events. Unfortunately these mechanical devices are exposed to salt water and the mechanical stresses attended such an exposed deployment dispose the devices to failure with the expected results. In addition, all the known interlock systems rely on the human element to one degree or another. Ideally, a mast deployment system should be constantly self-monitoring through a system of logic to automatically evaluate critical situations and circumvent improper extension and retrieval sequences that have damage potential. Having such a capability, the human element is discounted to assure more reliable operation.
Thus, there is a continuing need in the state of the art for an automatic electronic mast and closure actuation system which removes the human factor from an operational sequence and which is safely disposed within a submarine.